This is one in a series of interlinked experiments on the psychopharmacology of buprenorphine and naloxine. We are interested in studying buprenorphine because of its reported effect in the treatment of opiate dependence. However, bupreneorphine's mu opioid agonist effects has led to intravenous abuse in opiate-dependent populations. Combining buprenorphine with naloxone may diminish parenteral abuse liability. We will determine the relative and absolute bioavailability of a buprenorphine and naloxone combination tablet when administered orally and sublingually and measure its subjective and physiological effects. Subjects will be admitted to the GCRC one day prior to dosing and will be monitored for 48 hours post dose. The services we will need from the GCRC include clinical admitting procedures; obtaining clinical lab samples, as well as urine toxicology screens; placement of an IV catheter each session; monitoring vital signs at least one time per shift; collecting, processing, and packaging study-mandated urine and blood samples; and administering several subjective questionnaires. Performing these functions will aid in obtaining accurate study data which are vital for the successful completion of this study.